Molding materials of calcium silicate hydrate and shaped products thereof

ABSTRACT

A MOLDING MATERIAL OF CRYSTALLIZED CALCIUM SILICATE HYDRATE WHICH COMPRISES WATER AND CALCIUM SILICATE CRYSTALS DISPERSED IN THE WATER IN THE WEIGHT RATIO OF SOLID TO WATER OF BETWEEN 1:10 AND 1:25; AT LEAST 40 WEIGHT PERCENT OF SAID CALCIUM SILICATE CRYSTALS HAVING FORMED NUMEROUS SMALL AGGLOMERATES OF A DIAMETER OF 10 TO 150 MICRONS BY BEING THREE-DIMENSIONALLY INTERLOCKED WITH ONE ANOTHER; AND AGGLOMERATES BEING DISPERSED IN THE WATER IN SUBSTANTIALLY GLOBULAR FORM; A SHAPED PRODUCT OF CRYSTALLIZED CALCIUM SILICATE HYDRATE WHICH COMPRISES AGGLOMERATES OF CALCIUM SILICATE CRYSTALS BEING COMPRESSED TO AT LEAST ONE DIRECTION AND INTERLOCKED WITH ONE ANOTHER AND VOIDS INTERSPERSED THEREBETWEEN, SAID AGGLOMERATES HAVING HAD A DIAMETER OF 10 TO 150U.

BEST AVAEABLE COPY July 25, 1972 KAZUHIKO KUBO 3,679,445

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 1 F/&./

P: M220) X 1(002) 6- M002) 1(220) H 0.) B 5. 5 E .5 a k bulk derLSit](9/a) 0? Present shaped Products (No.5. l-6) XZCompafdZ/Vc? Shaped prud cfiwmflw) BEST AVAILABLE COPY July 25, 1972 KAZUHIKO KUBO 3,679,446

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 2 bulk density (31 0: Presentshaped Pr0dLLCZ(Nus '7-]Z) X A mpdralive Shape producm'lvbsfi 7-U2) BESTAVAILABLE COPY July 25, 1972 KAZUHIKOIKUBO 3,679,446

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 5 PZIDCZZMXHOOP.) 10(002)M220) Average value of opr/entation index a bulk densitflg ma) W resfntShaped Fr0dacZ,S(Nas./3-/S) X3 m neral/v6 s/za veoL pr0ducZS(Nm.C/3-C75)BEST AVAILABLE COPY y 25, 1972 KAZUHlKO KUBO 3,679,446

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 4 6- P: M220) 1(0021 M002)1(220) bulk density (9/0) BEST AVAILABLE CQPY July 25, 1972 KAZUHIKOKUBO 3,679,445

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 5 r 2 M320) M001) P M001) XIBT) o 0'5 (is bulk density 03 Present ,S/IZi DLd productSf/YuBI-Q) BESTAVAILABLE COPY y 25, 1972 KAZUHIKO KUBO MOLDING MATERIALS OF CALCIUMSILICATE HYDRATE AND SHAPED PRODUCTS THEREOF 9 Sheets-Sheet 6 Filed June2, 1969 01 resent shaped pr0ducts(/Vo.3l'-

, J l 25 1972 BEST AVAILABLE COPY KAZUHIKO KUBO 3,679,446 MOLDINGMATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTS THEREOF FiledJune 2, 1969 9 Sheets-Sheet 7 Average value of oriental/on index balkdensit m/ a) O Presc/zt ,Sfiaped/ producfS (/Va,:.37-4

BEST AVAILABLE COPY 25, 1972 KAZUHIKO KUBO 3,679,446

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 8 *7 P: M3202 X 001 Avcrayfivalue of orientation index T (A) buLk dens/t] (9/0216) O3 PrCsCnt ShapedprodwctS (Nos.43-48) BEST AVAILABLE COPY July 25, 972 KAZUHIKO KUBO3,679,445

MOLDING MATERIALS OF CALCIUM SILICATE HYDRATE AND SHAPED PRODUCTSTHEREOF Filed June 2, 1969 9 Sheets-Sheet 9 mi N bulk liensitmy aPrcscnt Shaped roducts(Nos.49-54) Y United States Patent O Int. Cl.C041) 1.5/06 US. Cl. 106-120 10 Claims ABSTRACT OF THE DISCLOSURE Amolding material of crystallized calcium silicate hydrate whichcomprises water and calcium silicate crystals dispersed in the water inthe weight ratio of solid to water of between 1:10 and 1:25; at least 40weight percent of said calcium silicate crystals having formed numeroussmall agglomerates of a diameter of 10 to 150 microns by beingthree-dimensionally interlocked with one another; and agglomerates beingdispersed in the water in substantially globular form; a shaped productof crystallized calcium silicate hydrate which comprises agglomerates ofcalcium silicate crystals being compressed to at least one direction andinterlocked with one another and voids interspersed therebetween, saidagglomerates having had a diameter of 10 to l50,u.

This invention relates to calcium silicate molding materials and shapedor molded products prepared therefrom.

It is Well known in the art that a siliceous material is reacted with acalcareous material in the presence of water at elevated temperatures toproduce calcium silicate hydrate. Various attempts utilizing such alime-silica reaction have been made for the formation of molded calciumsilicate products, particularly light-weight thermal insulatingmaterials. However, there are a number of dis advantages in the priorproducts and the processes of manufacture, as illustrated hereinbelow.

One general method heretofore employed is a so called pan castingmethod. According to this method shaped products of calcium silicatehydrate are prepared by mixing calcareous and siliceous materials withwater, with application of heat, to product amorphous calcium silicategel, pouring the gel thus obtained into a mold having an approximateshape of the final product desired, subjecting the gel while in the moldto an indurating step which is carried out in an autoclave under steampressure, whereby the gel undergoes a final chemical reaction to producehard mass of crystallized calcium silicate hydrate and drying the massremoved from the mold to produce the prodnot substantially free ofuncombined water.

Another typical method is a so called filter molding method, in whichexpanded amorphous calcium silicate gel prepared by reacting acalcareous material with a siliceous material in the presence of waterat 100 C. or thereabout is molded by a piston filter molding to producea self-supporting mass and the resultant mass removed from the mold isindurated in an autoclave under steam pressure, the indurated massthereafter being dried.

According to these methods it is difficult to produce a shaped producthaving uniform properties and excellent mechanical strength withlight-weight property unless the induration reaction is conducted for along period of time, as the amorphous calcium silicate gel is used as amolding material and subjected to the induration step while in the moldor after molding. Further the shaped product can ice not satisfactorilywithstand highly elevated temperatures. For example, the product mainlycomposed of tobermorite crystals is liable to decrease mechanicalstrength markedly at 650 C. or thereabout and to disintegrate or breakdown at over 700 C. And the product mainly composed of xonotlitecrystals tends to decrease the mechanical strength markedly at atemperature higher than about As evident from the description above,according to the prior processes it is indispensable to subject calciumsilicate gel used as a molding material to the induration step, andthere has been proposed no molding material capable of producing ashaped product of crystallized calcium silicate hydrate therefrom merelyby molding and drying without induration step under steam pressure.

One object of the invention is to provide a novel molding materialcapable of producing merely by molding and drying without anyapplication of steam pressure a shaped product of crystallized calciumsilicate hydrate having uniform and excellent properties and beinguseful for various purposes as thermal insulating materials, buildingmaterials, etc.

Another object of the invention is to provide a molding materialcontaining tobermorite crystals from which a shaped product oftobermorite crystals can be obtained merely by molding and drying.

A further object of the invention is to provide a molding materialcontaining xonotlite crystals from which a shaped product of xonotlitecrystals can be obtained merely by molding and drying.

A still further object of the invention is to provide a molding materialcontaining both tobermorite crystals and xonotlite crystals from which ashaped product of the both crystals can be obtained merely by moldingand drying.

Still another object of the invention is to provide a shaped product ofcalcium silicate crystals which is excellent and uniform in mechanicalstrength and resistance to heat.

A further object of the invention is to provide a shaped product oftobermorite, xonotlite or wallastonite crystals which has excellentmechanical strength as well as lightweight property and which is usefulas thermal insulating materials.

A further object of the invention is to provide a shaped product oftobermorite, xonotlite or wollastonite crystals which has highlyexcellent mechanical strength and is useful as building materials.

A further object of the invention is to provide a shaped product oftobermorite, xonotlite or wollastonite crystals free from deteriorationin mechanical strength at highly elevated temperatures.

These and other objects of the invention will be apparent from thefollowing description.

The molding material of the invention comprises water and calciumsilicate crystals dispersed in the water in the reight ratio of solid towater of between 1:10 and 1:25; at least 40 weight percent of saidcalcium silicate crystals having formed numerous small agglomerates of adiameter of 10 to microns by being three-dimensionally interlocked withone another; and said agglomerates being dispersed in the water insubstantially globular form.

The present inventor has so far carried out various experiments on amethod for manufacturing shaped products of calcium silicate hydrate andhas already filed United States of America patent application of Ser.No. 649,114, now US. Pat. No. 3,501,324, which relates to a method ofproducing a molding material containing calcium silicate hydrate and toa method of producing a shaped product of calcium silicate hydratetherefrom. The present inventor has further conducted researches on amolding material of crystallized calcium silicate hydrate from which ashaped product having high mechanical strength can be produced merely bymolding and drying without application of steam pressure. As a result,it has now been found that the calcium silicate aqueous slurries inwhich calcium silicate crystals are dispersed in the water in thespecific conditions as above enable the manufacture of molded productsof excellent mechanical strength merely by molding and drying withoutapplying any steam pressure, whereas it is known that the conventionalslurries of calcium silicate hydrate in which calcium silicate hydratedoes not form said specific agglomerates are difficult to produce moldedproducts of suflicient strength merely by molding and drying.

The calcium silicate crystals which constitute said specific agglomerateare platy crystals of tobermorite having a formula of 4CaO-5SIO -5H O or5CaO'6SiO -5H O, lathe-like crystals ofxonotlite having the formula of5CaO*5SiO -H O or 6CaO-6SiO -H O, or a mixture of the tobermorite andxonotlite crystals.

The aqueous slurry used as a molding material of the present inventioncontains calcium silicate crystals dispersed in the water in the weightratio of solid to water between 1:10 and 1:25, preferably between 1:11and 1:15. The calcium silicate crystals are three-dimensionallyinterlocked with one another to form a large number of smallagglomerates having 10 to O in diameter, whereby the objective shapedproduct of the present invention can be obtained merely by molding anddrying. The agglomerates, when smaller than 10 in diameter, make itdiflicult to carry out molding by a piston filter molding, while greateragglomerates exceeding 150p result in a shaped product which is poor inmechanical strength. The preferable particle diameter of the agglomerateranges from 30 to 90 However, it is not required that all of the calciumsilicate crystals in the slurry be in the form of agglomerates which are10 to 150g in diameter, but those agglomerates smaller than 10 or morethan 150a may also be involved in the slurry in less than a certainamount. By experiments the present inventor has found out that so far as40 weight percent of calcium silicate crystals dispersed in water are inthe form of agglomerates of 10 to 150 a shaped product superior to aconventional product in mechanical strength and heat resistance can beobtained merely by molding and drying.

In practical operation, it is desired that as many calcium silicatecrystals as possible be formed in agglomerates of 10 to 150 and the bestresults are attained with an aqueous slurry in which 90 to substantially100 weight percent of calcium silicate crystals are formed inagglomerates of 10 to 150,111..

The diameters of agglomerates given in the present specification andclaims are determined through inspection by optical microscope.

The above-mentioned proportion of the calcium silicate forming theagglomerates of 10 to 150 1. is determined by preparing an aqueousslurry in which substantially all of the calcium silicate crystals areformed in agglomerates of 10 to 150 mixing this slurry with anotheraqueous slurry of calcium silicate crystals having no above-mentionedagglomerates in various proportion and studying the molding property ofthe resultant slurry and physical prop erties of shaped productsobtained therefrom.

The aqueous slurry in which substantially all of the calcium silicatecrystals are formed in agglomerates of 10 to 150 can be produced byfulfilling the production conditions to be described later.

The above-mentioned agglomerates of 10 to 150 are formed of calciumsilicate crystals which are interlocked with one anotherthree-dimensionally in substantially globular shape. This is apparentlyappreciated in a dark ground micrograph of the slurry of the invention.That is, a great number of agglomerates, substantially globular inshape, can be observed in a dark ground micrograph taken at amagnification of diameters. Each agglomerate has numerous voids formedamong the crystals.

The process for manufacturing the aqueous slurry of the invention is ofa secondary significance and not critical in the invention, and anymethods capable of producing aqueous slurry as specified before areapplicable.

The basic technic of one preferred method for the production isdescribed in our patent application Ser. No. 649,114, now U.S. Pat. No.3,501,325, invented by the present inventor. In the above method astarting aqueous slurry of siliceous material calcareous material andwater is reacted with stirring under a saturated steam pressure of atleast 5 kg./cm. gauge to produce crystallized calcium silicate hydrate.

The siliceous material used may include, for example, amorphous silica,siliceous sand, diatomaceous earth, clays, silica gel, pozzollana,perlite, etc., and preferably one may be determined in accordance withthe desired calcium silicate crystals to be produced. For the selectiveproduction of xonotlite crystal, for example, those containing higherthan 90 weight percent of SiO component may be preferably used. As thepresence of A1 0 component in the siliceous material tends to preventthe selective production of xonotlite crystal, it is preferable to usesiliceous material containing no or less than 2 weight percent of A1 0most desirable being amorphous silica. For the selective production oftobermorite crystal the presence of impurities, such as A1 0 MgO, Fe Oetc., does not affect so adversely as in the case of the production ofxonotlite, and those containing more than 50 weight percent of SiO andless than 50 weight percent of the above impurities may be used. Thesiliceous material is used in the form of finely divided form passingthrough a 325 mesh screen. Preferable particle size is less than 5,u,most preferable being less than 0.2 The calcareous material used in theinvention may, for example, be quick lime, slaked lime, carbideresidium, etc. Of those, quick lime and slaked lime are preferable forthe production of xonotlite crystals, though various calcareousmaterial, such as carbide residue as well as quick lime and slaked limemay be used for the production oftobermorite.

The amount of the lime relative to the siliceous material may be in themolar ratio of CaOzSiO of between 0.65:1 and 13:1. The preferable ratiomay be selected in accordance with the crystaline structure to bedesired. Other reaction conditions, e.g., pressure temperature, reactionperiod may also efifect the crystalline structure to be produced.Therefore, by selecting these conditions tobermorite crystal, xonotlitecrystal or a mixture thereof can be selectively obtained. As far as theamount of the lime relative to the siliceous material is concerned, amolar ratio of CaOzSiO of between 0.65 :1 and 1:1 is preferable for theproduction of tobermorite crystal, and a molar ratio of that of between0.821 and 1.3:1 is preferable for the production of xonotlite crystal.Although the preferable ratio is overlapped, at such overlapped ratiotobermorite, xonotlite or a mixture thereof may be ob tained inaccordance with other reaction conditions applied. But when the ratio ofCaO to Si0 is less than 0.65:1 or that of CaO to SiO is higher than 1:1,it is not preferable for the production of tobermorite crystal, and whenthe ratio of CaO to S10 is higher than 1.321 or that of CaO to SiO isless than 0.8:1 it is undesirable for the production of xonotlitecrystal. Most preferable ratio of CaO to Si0 is 0.75:1 to 09:1 fortobermorite crystals and 0.95:1 to 1:1.1 for xonotlite crystals.

The amount of water used in the starting slurry is critical for theproduction of the desired aqueous slurry molding material of theinvention and may be used in such proportion as to produce the aqueousslurry of calcium silicate crystals having the weight ratio of solid towater of between 1:10 and 1:25, preferably between 1:11 and 1:15. Whenwater is used in less or larger amount it becomes difficult to produceagglomerates of 10 to failing to obtain the desired slurry of theinvention.

Inorganic fibers, such as asbestos, rock wool, glass fiber, etc., may beadded to the starting slurry for reinforcing purpose in an amount ofless than 50 percent, preferably of about to percent, based on theWeight of the total weight of the solids in the slurry, i.e., calcareousand siliceous materials used and reinforcing fibers added.

To accelerate the production of xonotlite crystal finely dividedWollastonite particles (CaO-Sio may be added to the starting aqueousslurry in 2 to Weight percent, preferably 5 to to 20 weight percent,based on the total Weight of the solids.

The starting slurry is heated with stirring under a steam pressure toproduce the hydrous calcium silicate aqueous slurry of the invention.The preferable stirring conditions can be determined with theconstitution of reactor, types of agitator, crystalline structure to beobtained, etc. According to the experiments of the present inventor ithas been found that when a cylindrical autoclave equipped with apaddle-type agitator is used as a reactor the preferable agitating speed(N) is evaluated from the following experimental equation:

2 D 3 N-N wherein N is a preferable agitating speed in terms of rpm. tobe determined, N is a revolution number per minute ranging from 75 to500, D is 0.14 in meter and D is an inner diameter in meter of thecylindrical autoclave used. For the production of aqueous slurry ofxonotlite crystals N is preferably a number ranging from 75 to 300, butfor the production of aqueous slurry of tobermorite or a mixture oftobermorite and xonotlite crystals N ranges from 75 to 500.

The steam pressure applied is usually higher than 5 l-:g./cm. gauge andthe higher the steam pressure, the shorter becomes the reaction period.Suitable reaction pressure may be selected in accordance with thecrystalline structure to be desired. For the production of tobermorite apressure of between 8 and 20 kg./cm. is preferable, and for xonotlite apressure of between 8 and 50 kg./cm. is preferable. The overlappedpreferable pressure for tobermorite and xonotlite have the samesignficance as that illustrated with respect to the amount and qualityof the starting siliceous material and calcareous material. The reactiontemperature is the saturated temperature under such saturated steampressure.

The period required to complete the reaction between lime and silicawill depend, for example, on reaction pressure and temperature, themixing ratio of the calcareous and siliceous materials and thecrystalline structure of calcium silicate hydrate to be desired. Ingeneral, the reation for the production of tobermorite may be completedin about 1 to 10 hours, and that for xonotlite is in about 0.5 to 20hrs. in accordance with the reaction conditions. The reaction vesselused is a pressure autoclave equipped with an agitator or stirrer andpressure gauge.

The aqueous slurry of the present invention may contain a reinforcingmaterial or some other additives. Applicable as reinforcing materialsare inorganic fibers such as asbestos fibers, rock wool, glass fibers orthe like, or organic fibers such as pulp fiber, wood flour, polyamidefibers, polyester fibers, or the like. With addition of these paterials,the shaped product obtained from the slurry of the invention can beremarkably improved in mechanical strength, particularly in bendingstrength. Most preferably asbestos may be used as a reinforcingmaterial. Inorganic fibers such as asbestos, rock Wool, etc. maypreviously be mixed with a starting aqueous slurry of calcereousmaterial and siliceous material as mentioned before, but the reinforcingmaterials may ordinarily be added directly to the aqueous slurry of theinvention. The aqueous slurry molding material obtained by the formermethod results in a shaped product which is superior in mechanicalstrength, especially in bending strength and less susceptible todeterioration in strength when subjected to high temperatures.Presumably, this is due to the interlocking of the reinforcing materialswith the agglomerates of calcium silicate crystals effected during thethermal hydration reaction, and this is more conspicuously effected whenasbestos is used as the reinforcing material. In a dark groundmicrograph taken at a magnification of 100 diameters showing the presentaqueous slurry prepared by the above-mentioned method with addition ofasbestos, a number of agglomerates are observed to tangle about asbestosfibers. In either of the foregoing methods, the reinforcing materialsare added in a proportion of less than 50 weight percent, preferably of5 to 20 weight percent based on the total weight of the solids in theslurry, namely of calcium silicate crystals and solid in the slurry ofcalcium silicate crystals and solid additives. Of reinforcing materialspulp fiber may be added in larger amount, i.e. up to weight percent,based on the total weight of the solids, for the production of buildingmaterials.

To the slurry of the present invention, various solid additives otherthan the reinforcing materials may also be added. The addition of clay,in particular, is advantageous in that the shaped product obtained isrendered more resistant to heat. As a clay for this purpose, bentonite,kaolin, pyrophylite, fire clay or the like may be employed, the range ofaddition being 3 to 50 weight percent, preferably 5 to 40 weight percentbased upon the weight of solids in the slurry.

Furthermore, in order to make the shaped product obtained from thepresent slurry more serviceable as buliding materials for certainpurposes by increasing its bulk density and hardness of the surface,cement may be mixed therewith. It is preferable to add cement in a rangeof from 5 to 60 percent, preferably from 10 to 50 percent, based on theweight of solids in the slurry.

To obtain a shaped product from the slurry of the present invention, theslurry, as it is or after it has been concentrated to a paste form, ismolded into a desired shape as, for example, in plate or bent form whilebeing subjected to dehydration to remove excess Water. The resultantproduct has only to be dried to substantially remove uncombined water.In this step filter molding may preferably be employed.

The filter molding comprises placing the present slurry in a female moldhaving a desired form and a plurality of small holes and pressing theslurry by a male mold to remove excess water until a self-supportingmass is formed, there being no substantial difference from aconventional method in which a molding material of calcium silicate gelis formed into a shaped product by the conventional filter molding.Further in case of a slurry containing pulp, the slurry is formed into asheet, which is then pressed into a molded product in sheet form bymeans of a paper machine and dried to obtain a finished product. Dryingcan be done at an atmosphere pressure and temperature, but under reducedpressure or by heating drying period can be reduced.

Thus the shaped product comprising tobermorite crystals or a mixture oftobermorite and xonotlite crystals can be obtained respectively from themolding material in the form of aqueous slurry containing thecorresponding crystals. The shaped product comprising wollastonitecrystals can be produced from the shaped product of xonotlite crystalsthus obtained by heating it a 800 to 1,050 C. to convert the xonotlitecrystals to fi-wollastonite.

The shaped product of the present invention is characterized by aspecific structure comprising agglomerates joined with one another andvoids interspersed among the agglomerates, the agglomerates being in theform compressed to the direction of pressure applied in the moldingstep. Namely, the agglomerates in the present shaped product arecompressed more or less in at least one direction due to the pressureapplied in the molding step. Since the agglomerates in themselves are ofconsiderable strength, they are not completely crushed unless subjectedto an exceedingly great molding pressure. The bulk density of a shapedproduct made of a slurry having no solid additives therein chieflydepends upon the pressure applied at the time of molding operation. Thatis to say, low molding pressure results in lower bulk density of ashaped product and high molding pressure in greater bulk density.Therefore, a shaped product having low bulk density is composed ofagglomerates which are compressed but not crushed. In fact, when thebroken surface of shaped product having bulk density (g./c1n. notexceeding 0.45 and formed from slurry without addition of additives ismagnified and observed through an optical microscope, the globularagglomerates are found to form shaped product as they are interlockedwith one another. The broken surface as herein used means a surfacewhich is formed by splitting a shaped product in two with carefulattention so as not to cut olf or destroy the agglomerates. Forinstance, the surface obtained by cutting the shaped product by a knife,even if magnified, no longer exhibit agglomerates. This can also beascertained by inspecting a transmission photograph showing the thinsection of the shaped product and taken at a right angle with thepressing directing at the time of molding. To obtain this picture, acube of 5 mm. x 5 mm. x 5 mm. in size having a plane at a right anglewith the pressing direction is cut off from a shaped product and thecube is impregnated with a styrene monomer under reduced pressure, theimpregnated cube thereafter being embedded with a resin in accordancewith embedding method to obtain a thin section a in thickness in themanner set forth in The Chemistry of Cement, vol. 2, pp. 235-236 (1964)edited by H. F. W. Taylor. The sample thus prepared is photographed toobtain a transmission photograph at a magnification of 120 diameters, inwhich a number of agglomerates appeared dark because of low transmissionof light, with the boundary thereof seen in white due to transmission oflight. The shaped product having a bulk density of not exceeding 0.45produced from a slurry containing no additives such as reinforcingmaterials has sufficient mechanical strength and heat-insulatingproperty, although a strong product has not been made by theconventional method without addition of reinforcing materials. A shapedproduct of this type having a bulk density in the order of 0.18 to 0.40is particularly useful as a heat-insulating material. With a shapedproduct in accordance with the present invention having a bulk densityof over 0.45 and containing no additives, it is difficult to identifythe agglomerates in the magnified photograph or transmission photograph.When diffracted by X-ray, however, such shaped product exhibits peculiarorientation, showing the agglomerates forming the shaped productcompressed strongly in the direction of pressure applied in the moldingstep. That is to say, when seen in an X-ray diffraction pattern showinga plane at a right angle with the pressing direction of the xonotliteshaped product of this type, diffracted intensity of (001) is greaterthan that of (320), while in case of the X-ray diffraction pattern of anon-oriented sample prepared from the above-mentioned shaped product,the intensity of (001) is always smaller than that of (320), thusshowing that the shaped product of the present invention presentsdistinct orientation. Such orientation cannot be found in a shapedproduct of calcium silicate crystals which is prepared in a conventionalmethod and commercially available. The shaped product of the presentinvention is characterized in that the average value of orientationindex (p) for shaped products of a mixture is greater than 2.0, theaverage value of orientation index of a conventional shaped product ofcalcium silicate being approximately equal to 1.0.

tobermorite crystals:

Orientation index (7)) for shaped product of xonotlite Orientation index(p) for shaped product of a mixture of tobermorite and xonotlitecrystals Orientation index (p) for shaped product of wollastonitecrystals =f:E 6 wherein I represents X-ray diffraction intensities of aplane at a right with the pressing direction of the shaped productaccording to the present invention and I represents X-ray diffractionintensities of the nonoriented sample prepared from the relevant shapedproduct of the present invention in accordance with Brindleys method forelimination of orientation as described in the American Mineralogist,Journal of Mineralogical Society of America, vol. 46, Nos. 11 and 12,pp. 1208-1209 (1961).

The average value of orientation index used in the present specificationand claims means the average value of the respective orientation indexeswhich are obtained by measuring ten samples taken out at random fromeach sample to be examined.

As apparent in the above equation, the average value of the orientationindex 2), when it is greater than 2.0, means that, in case, for example,of a shaped product of xonotlite crystals, the (001) plane of thecrystals is oriented to a considerably great extent in parallel with theplane which is at a right angle with the pressing direction of theshaped product, and when the average value of p is 1, it means that noorientation is effected.

In shaped products containing solid additives, such as reinforcingmaterials, clays and/ or cement, the bulk density thereof varies inaccordance with the kinds and amounts of the solid additives added aswell as the pressure applied in the molding step. Therefore, unlike in ashaped product free of solid additives, there exists no distinctdifference in characteristics due to the bulk density in case of suchshaped product. Of shaped products containing a substance such as cementwhich are great in specific gravity, regardless of whether their bulkdensities are more than 0.45, there are some whose agglomerates canreadily be identified in a magnified or transmission photograph showingthe broken surface or thin section, with the average value oforientation index less than 2.0. However, the shaped product which hasbeen compressed to such extent that the agglomerates thereof can not beidentified has an average value of the orientation index exceeding 2.0,even if the agglomerates can not be identified. In general, in case ofthose which have the average value of not exceeding 2.0, theagglomerates can be identified, whereas those having agglomerates whichcan not be identified have average value of orientation index over 2.0.

While the shaped products of wollastonite crystals which are prepared byheating the shaped products of xonotlite crystals, the agglomeratesforming the products are not broken and the specific orientationmentioned above is not changed substantially either by the heat appliedin their production. Thus all the present shaped products of tobermoritecrystals, xonotlite crystals, a mixture of tobermorite and xonotlitecrystals, or wollastonite crystals show the same trend as mentionedbefore in the form of the agglomerates and in the orientation.

The shaped products of the present invention give a number of advantagesas compared with the products prepared by the conventional method due tothe specific structure thereof which is characterised by the presence ofnumerous agglomerates jointed with one another and compressed in atleast one direction. The advantageous properties and usefulness of thepresent shaped products vary in accordance with the structures ofcrystals constituting each agglomerate forming the product, bulk densityof the product, absence or presence of solid additives, kinds of solidadditives if contained, etc., and they are summarized below.

In accordance with conventional pan casting method and filter moldingmethod, it was impossible to obtain light-weight and strong shapedproducts of tobermorite crystals, xonotlite crystals or a mixture ofboth of these crystals unless a reinforcing material such as asbestos isadded thereto, whereas the shaped products of the present inventionformed of the above-mentioned crystals, containing no reinforcingmaterial of such type, are light in weight and high in strength forpractical use. Thus, there is no need to use a relatively expensivereinforcing material like asbestos and in addition, the products arefree from various objections attributable to impurities contained inasbestos, especially to iron contents. For instance, a conventionalcalcium silicate product, in case where it is employed as aheat-insulating material in a cementation furnace, not infrequentlyresulted in destruction of the constituent members of the furnace due tothe fact that the iron contents in the asbestos causes higherdecomposition of carbon monoxide to produce deposition of carbon. Theuse of the shaped product of this invention which contains no asbestoseliminates such disadvantage.

Since the shaped product of the present invention is formed of theaqueous slurry of crystallized calcium silicate hydrate, shaped productscontaining various solid additives can be obtained depending upon theuses intended.

For instance shaped products containing reinforcing materials are higherin mechanical strength than those containing none of these materials andin case where the bulk density is low the products of the invention aremore excellent than conventional ones in mechanical strength, hencequite useful for heat insulating purposes.

The shaped product of the invention, when formed of a molding materialobtained from a starting slurry with asbestos fibers especially has ahigh mechanical strength by far superior to a conventional product, theinventive product being characterized by markedly low deteriora tion instrength and small contraction when subjected to heat. The shapedproduct greater in bulk density has a sufficiently high strength as abuilding material. For this purpose, organic fibers such as pulp fibersmay advantageously be used and the products containing the organicfibers are provided with greater strength than those without such fiberadditives. Moreover, they are useful as fireproof building materialsespecially for ceiling and partition since the pulp fibers therein donot burn when exposed to fire. Further in case where cement such asportland cement is included as a component it serves to improve theproduct not only in mechanical strength but also in hardness of surface,thus providing the product with a wider variety of uses.

A remarkable improvement is also achieved in shaped products whichcontain clays. That is to say, the products containing clays are higherin mechanical strength than those without clay additives and undergosmaller deterioration in strength and hardly any contraction.

Although a shaped product comprising wollastonite crystals was difiicutto produce and was not commercially available, a crack-free shapedproduct formed of wollastonite can be produced easily by firing thepresent shaped product of xonotlite crystals at a high temperature. Thisshaped product is hardly impaired in strength and shows only negligiblecontraction even when subjected to high heat of about 1000 to 1050 C. sothat it is ad- Bending strength IIS-A-9510 Coefiicient of linearcontraction JIS-A-9510 EXAMPLE 1 1-(1) Preparation of molding materialTo 20.3 liters of water was added 757 g. of quick lime for slaking, andto the resultant solution of slaked lime was added with stirring 933 g.of siliceous sand passing through a 325 mesh screen, whereby a startingaqueous slurry containing slaked lime and siliceous sand was obtained.Analysis of the siliceous sand used was as follows:

Percent Si0 91.91 A1 0 4.46 F6 0 Ig. loss 3.31

The starting slurry thus obtained was placed in an autoclave, 30 cm. indiameter and 40 cm. in depth, equipped with a paddle-type agitator andheated with stirring of 56 r.p.m. at 190.7 C. under a steam pressure of12 kg./cm. gauge for 5 hours. The autoclave was thereafter cooled toroom temperature and the resultant slurry was taken out therefrom. Thusthe aqueous slurry of calcium silicate crystals having a solidconcentration of 8.3% was obtained.

In X-ray diffraction, the crystals contained in the resultant slurryshowed a pattern peculiar to the tobermorite crystals at 11.4 A., 5.49A., 3.08 A., 2.98 A. and 2.82 A.

The slurry thus obtained contained numerous agglomerates dispersed inthe water. The agglomerates were globular in shape and had a particlesize of 20 to 70m. The same results were recognized when -diameter darkground micrographs of 10 portions of the above slurry taken out atrandom therefrom were inspected showing that almost all of the globularagglomerates had a particle size of 20 to 70 and that substantially allof the tobermorite crystals formed such agglomerates. Each agglomeratewas constituted by numerous tobermorite crystals interlocked with oneanother.

1-(2) Preparation of shaped product TABLE 1 Product No.: Bulk density 10.22 2 0.35 3 0.40 4 0.51 5 0.59 6 0.75

The structural characteristics of the resultant dried products wereascertained by a micrograph of the broken surface of each product, atransmission view of the thin section of each product and X-raydiffraction of each product.

FIG. 1 shows a graph of an average value of the orientation index ofeach product in relation to the bulk density thereof with thecomparative data of the shaped products prepared by Comparison 1 below.

COMPARISON 1 It was difiicult to produce calcium silicate productshaving bulk densities corresponding approximately to products Nos. 1 to6 by the conventional filter molding method using the same startingmaterials in Example 1-(1), and therefore the comparative products wereprepared in the following manner in which diatomaceous earth was used assiliceous material in place of siliceous sand.

1.25 kg. of quick lime was slaked in 50 liters of water warmed at 80 C.,to which was added with stirring 1.95 kg. of diatomaceous earth, and themixture was heated for 1.5 hours in an open vessel to produce calciumsilicate hydrate gel. Analysis of the diatomaceous earth used was asfollows.

Percent SiO 79.83 A1 9.67 P6203 CaO 3.46

MaO 0.37 Ig. loss 4.45

TABLE 2 Product No.: Bulk density C1 0.19

03 0.37 C-4 0.46 C-S 0.57 C-6 0.66

X-ray diffraction of each product showed the product comprisedtobermorite crystals, but many cracks occurred during the indurationstep.

The shaped product (No. 1) of the invention having a bulk density of0.22 was formed of numerous globular agglomerates jointed with oneanother. From a transmission view of the same product, it is observedthat a number of agglomerates forming the product are seen in darkbecause of low transmission of light with the boundary thereof in whitedue to transmission of light.

A micrograph of the broken section of the products Nos. 2 and 3 andtransmission view of these products shows the respective products wereformed of a number of agglomerates jointed with one another.

The presence of agglomerates was not recognized so exactly as above fromthe same inspection carried out by using the products Nos. 4 to 6 havinga bulk density of larger than 0.45, but the average value of theorientation index thereof gave the specific condition as shown inFIG. 1. From this figure it is seen that the average value oforientation index of the present products increases approximately inproportion to bulk density of the product and the products Nos. 4 to 6showed marked orientation exceeding 2.0 of the average value of theindex, while the value of the comparative products Nos. C-1 to C-6 wasapproximately 1.0, showing no orientation.

The mechanical strength of the present products Nos. '1 to 6 andcomparative products Nos. C-l to C-6 are shown in Table 3 following.

TABLE 3 Bending Bulk strength Product Number density (kg/cm?) 1Unmeasurable due to numerous cracks.

EXAMPLE 2 To 1117 parts of the aqueous slurry of tobermorite crystalsobtained in the same manner as in Example 1-(1) was added 70 parts of 10percent water dispersion of asbestos fiber and then mixed thoroughly.

Six kinds of shaped products having different bulk densities shown belowwere prepared in the same manner as in Example 1-(2) from the mixturethus obtained.

The structural characteristics of the resultant dried products wereinspected in the same manner as in Example 1-(2). From a micrograph ofthe broken surface of the products Nos. 7 to 9 having a bulk densityranging from 0.21 to 0.39, it was found that those products werecomposed of a large number of agglomerates jointed with one another andasbestos fibers. While almost no agglomerates were found in the productsNos. 10 to 12 having higher density in the same micrograph thereof, itwas ascertained by the measurement of the orientation index that suchproducts Nos. 10 to 12 exhibited a specific orientation as shown in FIG.2, in which the orientation indexes of the comparative products Nos. C-7to C-12 prepared by the method described in Comparison 2 below wereshown for comparative purpose.

COMPARISON 2 1.19 kg. of quick lime was slaked in 50 liters of waterwarmed at C., to which were added with stirring 0.231 kg. of asbestosfibers and 1.88 kg. of diatomaceous earth the same as in Comparison 1,and the mixture was heated at 97 C., for 1.5 hours in an open vessel toproduce calcium silicate hydrate gel. The gel thus obtained wasinspected through a dark ground micrograph taken at a magnification ofdiameters, but no agglomerates were observed.

The resultant gel was molded as in Comparison 1 and the molded mass wasindurated at 190.7 C. under a steam pressure of 12 kg./cm. for 5 hours,and then dried, producing six kinds of comparative products having thefollowing density.

TABLE 5 Product No.: Bulk density C-7 0.20

C 10 0.51 C-ll 0.60 -C-12 0.68

X-ray diffraction of each product showed the product comprisedtobermorite crystals.

Frim FIG 2 it is seen that the average value of orientation index of thepresent products increases approximately in proportion to bulk densityof the product and the products Nos. to 12 showed marked orientationexceeding 2.0 of the average value of the index, while the value of thecomparative products Nos. C-7 to C-12 was approximately 1.0, showing noorientation.

The mechanical strength and heat resistance of the products were shownin Table 6 below.

14 the orientation indexes of the comparative products Nos. C-13 to C-18prepared by the method described in Comparison 3 below were shown forcomparative purpose.

COMPARISON 3 1.06 kg. of quick lime was slaked in 50 liters of waterwarmed at 80 C., to which were added with stirring 0.56

TABLE 6 After preparation After 3 l1rs.firing at 650 C. After 3 hrs.firing at 800 C.

Coefficient Coefllcient Bending Bending of linear B ending of linearProduct Bulk strength strength contraction strength contraction N0.density (kg/cm?) (kg/cm?) (percent) (kg/cm?) (percent) 1 Broken.

EXAMPLE 3 To 997 parts of the aqueous slurry of tobermorite crystalsobtained in the same maner as in Example 1 was added 170 parts of 10%water dispersion of pulverized bentonite passing through a 325 meshscreen and then mixed thoroughly. The analysis of the bentonite usedgave the following results:

Percent SiO 73.84 A1 0 13.24 Fe O 1.29 Ig. loss 3.46

From the resultant mixture were produced in the same manner as inExample 1 six kinds of shaped products having dilferent bulk densitiesshown below.

The structural characteristics of the resultant dried products wereinspected in the same manner as in Example 1. From a micrograph of thebroken surface of the products Nos. 13 to 15 having a bulk densityranging from 0.20 to 0.41, it was found that those products were kg. ofbentonite and 1.68 kg. of diatomaceous earth the same as in Comparison1, and the mixture was heated in an open vessel at 97 C. for 1.5 hoursto produce calcium silicate hydrate gel. The gel thus obtained Wasinspected in a dark ground micrograph taken at a magnification of 120diameters, but no agglomerates were observed.

Six kinds or" shaped pro-ducts having diiferent densities shown belowwere prepared in the same manner as in Comparison 2 from the resultantgel.

TABLE 8 Product No.: Bulk density C-13 0.18 C-l4 0.28 C-lS 0.37 C-160.48 C-17 0.56 C-18 0.65

X-ray diffraction showed that crystalline structure of each product wastobermorite, but many cracks occurred in the products during indurationstep.

From FIG. 3 it is seen that the orientation index of the presentproducts increases approximately in proportion to bulk density of theproduct and the products Nos. 16 to 18 show marked orientation exceeding2.0 of the average value of the index, while the value of thecomparative products Nos. C-13 to C18 was approximately 1.0, showing noorientation.

The mechanical strength and heat resistance of the products are shown inTable 9 below.

TABLE 9 Coelficient Coefficient Bending Bending of linear Bending oflinear Product Bulk stren th strength contraction strength contractionNo. density (kg/cm (kg/cm?) (percent) (kg/cmfl) (percent) lvUnmeasurable for numerous cracks.

EXAMPLE 4- T0 913 parts of the aqueous slurry of tobermorite crystalsobtained in the same manner as in Example 1-( 1) were added 70 parts of10% water dispersion of asbestos fiber and parts of 10% water dispersionof bentonite the same as in Example 3 and then mixed thoroughly.

15 Six kinds of shaped products having different bulk densities shownbelow were prepared in the same manner as in Example 1 from theresultant mixture.

16 X-ray diffraction of the resultant product showed that thecrystalline structure thereof was tobermorite. From FIG. 4 it is seenthat the orientation index of the present products increasesapproximately in proportion to bulk TABLE 10 Product No Bulk densitydensity of the product and the products Nos. 22 to 24 19 022 show markedorientation exceeding 2.0 of the average 20 031 value of the index,while the value of the comparative 21 40 products (products Nos. C-19 toC-24) was approxi- 22 Q49 mately 1.0, showing no orientation.

23 0,60 The mechanical strength and heat resistance of the 24 0.71products were shown in Table 12 below.

TABLE 12 After preparation After 3 hrs. firing at 650 C. After 3 hrs.firing at 810 C.

Coeflicient Coetficient Bending Bending of linear Bending of linearProduct Bulk strength strength contration strength contraction N 0.density (kg. lemfi) (kg. lcmfl) (percent) (kg/01m (percent) 0. 22 5. s44. 75 0. 67 4. 54 1. 63 0. 31 10. 50 9.25 0. 67 8.71 1. 33 0. 40 18.5015. 00 0.63 13. 42 1. 0. 49 25. 20. 20 0.63 0. 60 32. 30. 20 0.63 0.7135. 3o 31. 30 0. 68 0. 19 4. 62 2. 43 1. 06 o. 30 6. 32 3. 31 1. 63 0.39 11. 06 4. 2s 1. 60 0. 47 20. 90 10.20 1. 63 0. 5s 2s. 89 15. 21 1.60o. 65 as. 20 19. 42 1. 52

Broken.

The structural characteristics of the resultant dried EXAMPLE 5 Productswere Inspected m the same manner m 40 To 20.3 liters of water were addedquick lime and siliample 1. From a micrograph of the broken surface ofthe products Nos. 19 to 21 having a bulk density ranging from 0.22 to0.40, it was found that those products were composed of large number ofagglomerates jointed with one another and asbestos fibers and pulverizedclay dispersed therein. While almost no agglomerates were found in theproducts Nos. 22 to 24 having higher density through the same micrographthereof, it was ascertained by the measurement of the orientation indexthat such products Nos. 22 to 24 exhibited a specific orientation asshown in FIG. 4, in which the orientation indexes of the comparativeproducts Nos. C-19 to C-24 prepared by the method described inComparison 4 below were shown for comparative purpose.

COM PARIS ON 4 0.97 kg. of quick lime was slaked in 50 liters of waterwarmed at 80" C., to which were added 0.23 kg. of asbestos fibers, 0.56kg. of bentonite the same as in Comparison 3 and 1.54 kg. ofdiatomaceous earth, and the resultant mixture was heated in an openvessel at 97 C. for 1.5 hours to produce calcium silicate hydrate gel.The gel thus obtained was inspected in a dark ground micrograph taken ata magnification of 120 diameters, but no agglomerates were observed.

The resultant gel was molded and indurated in the same manner as inComparison 2, producing six 'kinds of products having the following bulkdensities.

TABLE 11 Product No.: Bulk density C-19 0.19 C-20 1 0.30 C-2l 0.39

C-22 11111111 a 0.47 C-23 0.56 (3-24 PM 0.65

ceous sand the same as in Example 1 in the amounts shown in Table 13 andthe mixture was thoroughly mixed to produce six kinds of startingslurries.

Each starting slurry thus obtained was placed in an autoclave, 30 cm. indiameter and 40 cm. in depth, equipped with an agitator and heated withstirring of 60 rpm. at 187 C. under a steam pressure of 11 kg./cm. gaugefor 5 hours. Thus 6 kinds of the aqueous slurries of calcium silicatecrystals having a solid concentration of 8.3 percent were obtained.

By X-ray diffraction the crystals contained each resultant slurry showedthe pattern peculiar to the tobermorite crystals at 11.4 A., 5.49 A.,3.08 A. and 2.98 A. A dark ground micrograph and electron micrograph ofeach resultant slurry show that the slurry contained numerousagglomerates, globular in shape, having a particle size of 20 to 7 Onwhich was constituted with numerous platelike tobermorite crystalsinterlocked with one another.

913 parts of the respective slurries were mixed with 70 parts of 10%water dispersion of asbestos fiber and parts of 10% water dispersion ofbentonite, from which shaped product were prepared in the same manner asin Example 1, with the results shown in Table 14 following.

TAB LE 14 Aiter 3 hrs. firing at 650 C.

Slurry Coefiiclent used Bending Bending of linear (slurry Bulk strengthstrength contraction Product number Number) density (kg/0111. (kg/cm(percent) S-1 0. 178 3. 83 3. 77 0. 54 S-2 0. 197 3. 81 3. 57 0. 80 S-30. 190 3. 92 3. 03 0. 80 S-4 0. 198 4. 21 3. 65 0. 67 S-5 0.183 5. 57 5.50 0. 47 3 S-6 0. 204 5.80 3. 45 0. 63

Through the inspection of a micrograph of the broken surface of eachshaped product thus obtained it was ascertained that it was formed ofnumerous agglomerates jointed with one another.

EXAMPLE 6 6-(1) Preparation of molding material Percent S10 96.97 A1 01.39 Fe 0 0.07 Ig. loss 0.93

The starting slurry thus obtained was placed in an autoclave, 30 cm. indiameter and 40 cm. in depth, equipped with a paddle-type agitator andheated with stirring of 56 r.p.m. at 187 C. under steam pressure of 11kg./cm. gauge for 10 hours. Thus the aqueous slurry of calcium silicatecrystals having a solid concentration of 8.3 percent was obtained.

In X-ray diffraction of the crystals contained in the resultant slurrygave the specific pattern to the xonotlite crystal at 7.80 A., 3.23 A.,3.08 A., and 2.83 A. A dark ground micrograph of the resultant slurrytaken at a magnification of 120 diameters and an electron micrographtaken at a magnification of 13,000 diameters show the agglomerates inthe slurry.

It is evident that the slurry thus obtained contained numerousagglomerates dispersed in the water and the agglomerates, globular inshape, had a diameter of 40 to 150p. While 120-diameter dark groundmicrograph of 10 portions of the above slurry taken out at randomtherefrom was inspected, they showed almost all of the globularagglomerates had particle size 40 to 150,4; and that substantiallyalmost all of the xonotlite crystals formed such agglomerates. Eachagglomerate comprised numerous xonotlite crystals interlocked with oneanother.

6-(2) Preparation of shaped product TABLE 15 Product No.: Bulk density31 0.21 32 0.30 33 0.41 34 0.50 35 0.61 36 0.70

The structural characteristics of the resultant dried products wereascertained by a microscopic view of the broken surface of each product,a transmission view of the thin section of each product and X-raydifiraction of each product.

FIG. 5 shows a graph of an average value of the orientation index ofeach product in relation to the bulk density thereof.

The shaped product (No. 31) of the invention having a bulk density of0.21 was formed of numerous globular agglomerates jointed with oneanother. From the transmission view of the same product, it is observedthat a number of agglomerates forming the produced appeared dark becauseof low transmission of light with the boundary thereof seen in white dueto transmission of light.

The micrograph of the broken section of the products Nos. 32 and 33 andtransmission view of these products, show the respective products wereformed of a number of agglomerates jointed with one another.

The presence of agglomerates were not recognized so exactly as abovefrom the same inspection carried out by using the products Nos. 34 to 36having a bulk density of larger than 0.45, but the average value of theorientation index thereof gave the specific condition as shown in FIG.5.

From FIG. 5 it is seen that the average value of orientation index ofthe present products increases approximately in proportion to bulkdensity of the product and the products Nos. 34 to 36 exhibited markedorientation exceeding 2.0 of the average value of the index.

The mechanical strength and heat resistance of the products were shownin Table 16 below.

TABLE 16 After 3 hrs. firing at 1,000 C. After preparation CoefiicientThe X-ray difiraction of the respective shaped products in the aboveexamples subjected to firing at 1000 C. for 3 hours showed that thexonotlite crystals forming the shaped body have all transformed into 13-wollastonite crystals. The micrograph of the broken surface taken at amagnification of diameters of products Nos. 3133 subjected to firing and120-diameter transmission images of thin sections of the same coincidedwith those of products Nos. 31-33 taken before firing. Accordingly itwas recognized that only the constituent crystals were transformed intoB-wollastonite without the agglomerates being destroyed. Furthermore,with respect to the fired products of products Nos. 34-36, the sameimages thereof hardly showed any agglomerates as with those of the sameproducts before firing, but exhibited distinct orientation. The

19 average values of orientation index of the respective products areillustrated in FIG. 6.

Thus, the shaped products in which only the xonotlitc crystals have beentransformed into wollastonite crystals 20 EXAMPLE 8 To 997 parts of theaqueous slurry of xonotlitecrystals obtained in the same manner as inExample :6 was added 170 parts 10% water dispersion of bentonite thesame as have characteristics that they are not impaired strength inExample 3 and then mixed thoroughlydo they even w i gg ig 9 From theresultant mixture were prepared in the same high .tempemmr? o appmma e yo manner as in Example 6 six kinds of shaped products hav- Thls apparentm Table 17 below ing different bulk densities shown below.

TABLE 17 After 3 hrs. firing at 1,o00 0.

Product Coeflicient number Bending Bending of linear before Bulkstrength strength contraction Product No. firing density (kg/cm (kg/cm(percent% 31 0. 21 4. 74 4. 70 0. 32 0. 29 9. 20 s. 91 o. 03 33 0. 3913. 13. 00 o. 0 34 0. 50 15. so 14. so 0. 0 35 0. 60 21. 20. 10 0. 0 as0. s9 30. 29. 50 0. 0

EXAMPLE 7 TABLE 20 Product No.: Bulk density To 1117 parts of theaqueous slurry of xonotlite crys- 95 4 (H9 tals obtained in the samemanner as in Example 6 were e 4, 029 added 70 parts of 10% waterdispersion of asbestos fibers 45 0A0 and then mixed thoroughly. 46 0.49Six kinds of shaped products having different bulk 47 050 densitiesshown below were produced in the same manner 30 4 071 as m Examp 1e 6from the resultant mature The structural characteristics of theresultant dried prod- TABLE 18 ucts were inspected by the same manner asin Example product Bulk density 6. From a photomicrograph of the brokensurface of the 37 020 products Nos. 43 to 45 having a bulk densityranging 38 030 from 0.19 to 0.40, it was found that those products com-39 0'40 prised large number of agglomerates jointed one another 40 51and y p s d thercln. While almost no agglomerates 41 060 were found inthe products Nos. 46 to 48 having higher 42 Q69 Q Y through the ammlcrograph thereof, it was ascer- 40 tamed by the measurement of theorientation index that The structural characteristics of the resultantdried P Proclucts N 46 f0 43 eXhibited a Specific Orientaproducts wereinspected by the same manner as in Exas 111 m F G. 8 it is seen that theample From a micrograph of the broken surface f orientation index of thepresent products increases apthe products Nos. 37 to 39 having a bulkdensity ranging PTOXlmatelY 111 P OPOIUOII u k density of the product f02 to 040 it was f d that those products 45 and the product Nos. 46 to48 show marked orientation prised a large number of agglomerates jointedwith one exceeding f the average lue of the index. another and asbestosfibers dispersed therein. While al- The mechamcal stfength and heatresistance of the most no agglomerates were found in the products Nos.Products were Shown mTable 21 below. 40 to 42 having higher density inthe same micrograph thereof, it was ascertained by the measurement ofthe 50 TABLE 21 orientation index that such products Nos. 40 to 42 ex-AM ah firi t hibited a specific orientation as shown in FIG. 7. Afterpreparation 1,058 0. nga

From FIG. 7 it is seen that the orientation index of C m m the presentproducts increases approximately in propor- Bulk Btendiltlg B endn i 15ili l l enr tion to bulk density of the roduct and the products Nos. 5 sS Hills 0 co raction 40 to 42 show marked orientation exceeding 2.0 ofthe denslty (kg'lcm'z) (percent) average value of the index. 8: 1g 3 1;8' The mechanical strength and heat resistance of the :5 8:32 0189product were shown in Table 19 below. 81%?) 381% 33 3:39 0.71 48. so as.20 o. 92

TABLE 19 After 3 hrs. firing at After preparation 1,000 C.

Coefficient Bending Bending of linear Product Bulk strength strengthcontraction number density g./cm (kg/cm!) (percent) The X-raydiffraction, IZO-diameter images of the broken section and l20-diametertransmission images of the respective shaped products in the aboveExample 8 which were fired at 1000 C. for 3 hrs. showed results similarto those obtained with respect to the products in Example 6 fired at1000 C. for 3 hours. Thus, it was recognized that these shaped productswere formed of ,o-wollastonite crystals as the fired products in Example6.

The bending strength of the products and the bending strength andcoefiicient of linear contraction after further firing at 1000 C. for 3hrs. of the same are given in the table following.

TABLE 23 Product No.: Bulk density 49 0.17

The structural characteristics of the resultant dried products wereinspected by the same manner as in Example 6. From a micrograph of thebroken surface of the products Nos. 49 to 51 having a bulk densityranging from 0.17 to 0.39, it was found that those products, comprised22 EXAMPLE 10 To 20.3 liters of water were added quick lime andamorphous silica the same as in Example 6 in the amounts shown in Table25 and the mixture was thoroughly mixed to produce six kinds of startingslurries.

Each starting slurry thus obtained was placed in an autoclave, 30 cm. indiameter and 40 cm. in depth, equipped with an agitator and heated withstirring of 60 r.p.m. at 187 C. under a steam pressure of 11 kg./cm.

gauge for 10 hours. Thus 6 kinds of the aqueous slurries of calciumsilicate crystals having a solid concentration of 8.3 percent wereobtained.

The X-ray diifraction of the crystals contained in each resultant slurrygave strong patterns at 7.08 A., 3.23 A., 3.08 A. and 2.83 A., showingthe crystals having xonotlite crystalline structure. The dark groundmicrograph and electron micrograph of each resultant slurry show thatthe slurry contained numerous agglomerates having a particle size of to150 which comprised numerous lathe-like xonotlite crystals interlockedwith one another.

913 parts of the respective slurries were mixed with 70 parts of 10%water dispersion of asbestos fibers and 170 parts of 10% waterdispersion of bentonite and shaped products were prepared therefrom inthe same manner as in Example 6, with the results shown in Table 26below.

larger number of agglomerates jointed with one another and asbestosfiber and clay dispersed therein. While almost no agglomerates werefound in the products Nos. 52 to 54 having higher density through thesame micrograph thereof, it was ascertained by the measurement of theorientation index that such products Nos. 52 to 54 exhibited a specificorientation as shown in FIG. 9. From FIG. 9 it is seen that theorientation index of the present products increases approximately inproportion to bulk density of the product and the products Nos. 52 to 54show marked orientation exceeding 2.0 of the average value of the index.

The mechanical strength and heat resistance of the products were shownin Table 24 below.

tained to be formed with numerous agglomerates jointed with one another.

EXAMPLE 11 To 20.30 liters of water was added 757 g. of quick lime forslaking and to the resultant solution of slaked lime was added 933 g. ofamorphous silica the same as in Example 6 to produce a starting slurry.

The starting slurry thus obtained was reacted in the same manner as inExample 6 except that the slurry was heated at 194 C. under a steampressure of 13 kg./cm. for 3 hours, producing an aqueous slurry ofcalcium silicate crystals having a solid concentration of 8.3%.

The X-ray difiraction of the crystals contained in the slurry gave apattern peculiar to tobermorite and xonotlite crystals, and thus thecrystals were ascertained a mixture of both crystals. The dark groundmicrograph and electron micrograph of each resultant slurry showed thatthe slurry contained numerous agglomerates, globular in shape, having aparticle size of 20 to which was constituted from numerous plate-liketobermorite crystals and lathe-like xonotlite crystals interlockedthree-dimensionally with one another.

